上个月发布了一个WP8.1应用：NuGet Search，并在GitHub开了源:https://github.com/EdiWang/WP-NuGetSearch

NuGet的服务接口是个WCF OData Service，为了装逼，我尝试使用了跨Framework的PCI工程，结果no zuo no die了。和一般.NET类库不同，PCL有些tricky的地方要爆。下面是开荒成功的代码：

public async Task>> GetDataAsync(string searchTerm, int pageIndex, bool includePreRelease = false)
 {
     try
     {
         IDictionary queryOptions = new Dictionary {
             { "filter", "IsLatestVersion" },
             { "searchTerm", "'" + UrlEncodeOdataParameter(searchTerm) + "'" },
             { "includePrerelease", includePreRelease.ToString().ToLower() }
         };
 
 
         if (pageIndex < 1)
         {
             pageIndex = 1;
         }
 
 
         int startRow = (pageIndex - 1) * PageSize;
         var nquery = context.CreateQuery("Search")
                             .OrderByDescending(p => p.DownloadCount)
                             .Skip(startRow)
                             .Take(PageSize);
 
 
         var query = (DataServiceQuery)nquery;
         if (queryOptions.Any())
         {
             query = queryOptions.Aggregate(query, (current, pair) => current.AddQueryOption(pair.Key, pair.Value));
         }
 
 
         var taskFactory = new TaskFactory>();
         var result = await taskFactory.FromAsync(query.BeginExecute(null, null), query.EndExecute);
         var packages = result.ToList();
 
 
         return new Response>()
         {
             IsSuccess = true,
             Item = packages
         };
     }
     catch (Exception e)
     {
         return new Response>()
         {
             Message = e.Message
         };
     }
 }

需要注意的：

1. 对于非标准的操作符，需要使用“AddQueryOption()”方法把它们撸进去，就像我代码里一样，用了个字典包装这些参数

IDictionary queryOptions = new Dictionary {
    { "filter", "IsLatestVersion" },
    { "searchTerm", "'" + UrlEncodeOdataParameter(searchTerm) + "'" },
    { "includePrerelease", includePreRelease.ToString().ToLower() }
};

2. 由于OData Client的PCL版本只支持异步操作，但它又没暴露基于Task的异步方法（你^TM在逗我？），我们只能用TaskFactory把IAsyncResult撸成awaitable的Task

var taskFactory = new TaskFactory>();
var result = await taskFactory.FromAsync(query.BeginExecute(null, null), query.EndExecute);

3. 对于标准LINQ操作，OData库可以正确翻译到URL，所以可以放心写这样的查询语句：

var nquery = context.CreateQuery("Search")
                    .OrderByDescending(p => p.DownloadCount)
                    .Skip(startRow)
                    .Take(PageSize);

翻译后的URL：

https://www.nuget.org/api/v2/Search()?$orderby=DownloadCount
desc&$skip=0&$top=30

带参数字典的：

https://www.nuget.org/api/v2/Search()?$orderby=DownloadCount
desc&$skip=0&$top=30&filter;=IsLatestVersion&searchTerm;=''&includePrerelease;=false

4. Response格式的例子：

  https://www.nuget.org/api/v2/curated-feeds/microsoftdotnet/Search
  
  2014-06-01T02:31:18Z
  
  
    https://www.nuget.org/api/v2/curated-feeds/microsoftdotnet/Packages(Id='EntityFramework',Version='6.1.0')
    
    
    
    
Entity Framework is Microsoft's recommended data access technology for new applications.
    2014-05-20T18:39:08Z
    
      Microsoft
    
    
    
    
      6.1.0
      6.1.0
      
      2014-03-17T21:38:19.813
      
      Entity Framework is Microsoft's recommended data access technology for new applications.
      5345924
      https://www.nuget.org/packages/EntityFramework/6.1.0
      http://go.microsoft.com/fwlink/?LinkID=386613
      true
      false
      false
      en-US
      2014-03-17T21:38:19.877
      u/M0OEfqxTUsL5BwzD66eBGm278/ozqdLK3JvMO6QwUxxc+z7ZUkTYm4suDhWRqzkc6mOhvXDQY5dZUwbldxyQ==
      SHA512
      4222059
      http://go.microsoft.com/fwlink/?LinkID=320540
      https://www.nuget.org/package/ReportAbuse/EntityFramework/6.1.0
      
      true
      Microsoft EF Database Data O/RM ADO.NET
      EntityFramework
      345877
      
      
      http://go.microsoft.com/fwlink/?LinkID=320539
      
      
    
  
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